The invention relates to a projection data acquisition apparatus (31) for acquiring projection data. The projection data acquisition apparatus comprises a radiation device (32) for generating a pulsed radiation beam (4) for traversing an object and a detection device (6) for generating projection data being indicative of the pulsed radiation beam (4) at different acquisition positions wherein the radiation device (32) is adapted to generate the pulsed radiation beam (4) such that at different acquisition positions the pulsed radiation beam (4) has different shapes i.e. is differently blocked and/or attenuated. Thus not the complete radiation providable by the radiation device is used at each acquisition position but at least at some acquisition positions only a smaller pulsed radiation beam is used. This can lead to less scattered radiation and hence to improved projection data and an improved computed tomography image which may be reconstructed based on the acquired projection data.
